Fix register allocation on x86

Fixes oss-fuzz #43119

Author: dstogov

ext/opcache/jit/zend_jit_x86.dasc

@@ -6039,6 +6039,7 @@ static int zend_jit_simple_assign(dasm_State    **Dst,
 				val_addr = ZEND_ADDR_MEM_ZVAL(ZREG_R2, 0);
 			} else {
 				zend_jit_addr ref_addr;
+				zend_reg type_reg = tmp_reg;
 
 				if (in_cold) {
 					|	IF_NOT_ZVAL_TYPE val_addr, IS_REFERENCE, >1
@@ -6047,21 +6048,24 @@ static int zend_jit_simple_assign(dasm_State    **Dst,
 					|.cold_code
 					|1:
 				}
-				if (Z_REG(val_addr) == ZREG_R2) {
-					|	mov aword T1, r2 // save
-				}
 				|	// zend_refcounted *ref = Z_COUNTED_P(retval_ptr);
 				|	GET_ZVAL_PTR r2, val_addr
 				|	GC_DELREF r2
 				|	// ZVAL_COPY_VALUE(return_value, &ref->value);
 				ref_addr = ZEND_ADDR_MEM_ZVAL(ZREG_R2, 8);
 				if (!res_addr) {
-					|	ZVAL_COPY_VALUE var_addr, var_info, ref_addr, val_info, ZREG_R2, tmp_reg
+					|	ZVAL_COPY_VALUE var_addr, var_info, ref_addr, val_info, type_reg, tmp_reg
 				} else {
-					|	ZVAL_COPY_VALUE_2 var_addr, var_info, res_addr, ref_addr, val_info, ZREG_R2, tmp_reg
+					|	ZVAL_COPY_VALUE_2 var_addr, var_info, res_addr, ref_addr, val_info, type_reg, tmp_reg
 				}
 				|	je >2
-				|	IF_NOT_REFCOUNTED dh, >3
+				if (tmp_reg == ZREG_R0) {
+					|	IF_NOT_REFCOUNTED ah, >3
+				} else {
+					|	IF_NOT_FLAGS Rd(tmp_reg), IS_TYPE_REFCOUNTED, >3
+				}
+				|	GET_ZVAL_PTR Ra(tmp_reg), var_addr
+
 				if (!res_addr) {
 					|	GC_ADDREF Ra(tmp_reg)
 				} else {
@@ -6070,17 +6074,19 @@ static int zend_jit_simple_assign(dasm_State    **Dst,
 				|	jmp >3
 				|2:
 				if (res_addr) {
-					|	IF_NOT_REFCOUNTED dh, >2
+					if (tmp_reg == ZREG_R0) {
+						|	IF_NOT_REFCOUNTED ah, >2
+					} else {
+						|	IF_NOT_FLAGS Rd(tmp_reg), IS_TYPE_REFCOUNTED, >2
+					}
+					|	GET_ZVAL_PTR Ra(tmp_reg), var_addr
 					|	GC_ADDREF Ra(tmp_reg)
 					|2:
 				}
-				if (Z_REG(val_addr) == ZREG_R2) {
-					|	mov r2, aword T1 // restore
-				}
 				if (save_r1) {
 					|	mov aword T1, FCARG1a // save
 				}
-				|	EFREE_REFERENCE aword [Ra(Z_REG(val_addr))+Z_OFFSET(val_addr)]
+				|	EFREE_REFERENCE r2
 				if (save_r1) {
 					|	mov FCARG1a, aword T1 // restore
 				}

ext/opcache/tests/jit/assign_049.phpt

@@ -0,0 +1,29 @@
+--TEST--
+JIT ASSIGN: register allocation on x86
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+opcache.protect_memory=1
+--FILE--
+<?php
+function &a($i) {
+    $a = "str". $i;
+    return $a;
+}
+
+class A {
+    public $a;
+    public function test() {
+        $this->a = a(1);
+    }
+}
+
+$a = new A;
+$a->test();
+$a->test();
+?>
+DONE
+--EXPECT--
+DONE